Several million persons in the United States are currently living with implanted cardiac rhythm management devices (CRMDs); a few hundred thousand new devices are implanted annually (1). The majority of these patients are older than 60 years. As the long-term survival of this population improves and utilization of CRMDs continues to grow (2), the probability increases that many of these patients will encounter medical situations for which magnetic resonance imaging (MRI) may be useful, or even critical, for optimal diagnosis and treatment. This likelihood is difficult to assess because the value of MRI relative to alternatives may vary, but estimates of greater than 50% have been published (3).